Asphaltic material and method of preparing same



T proportion in a Patented-Sept. 25, 19 2s.

. umrn' WILLIAM 0. WEST, OF LOUISVILLE, KENTUCKY, ASSIGNOR T0 WESTPROCESS PAVE- ncnnr' comm, INCORPORATED, or

OF KENTUCKY.

LOUISVILLE, I IENTUCKY, A CORPORATION ASPHALTIG MATERIAL AND METHOD OFPREPARING SAME.

No Drawing. Application filed Match This inventionrelates' to 'asphalticmaterials and the novel methods by which the same are prepared, and hasfor its object to provide a material containing the required amounts ofmineral aggregate, filler, and asphalt and which may be prepared in itsentirety at a central plant and shipped Sheet asphalt pavements consistof sand usually graded to meet certain specifications, to which is added'a'specified' amount of limestone dust or other impalpable' powder as afiller, and a' given percentage of asphalt cement meeting certainspecifications as to penetration or hardness, loss by heating, parafiinecontent, etc. The mineral aggregate and the asphalt, cement are heatedseparately and mixed together in the right ug-mill. The material is thenhauled to the point at which it is to be laid and must arrive there at atemperature well above 250 and be raked and.

rolled while hot. A disadvantage (if this type of pavement is that anycontractor who desires to bid on and construct such a pavement must havebetween $30,000 and $75,000 invested in a hot-mix plant. This necessaryinvestment, of course, will keep out the small but equally eflicientcontractor and lessen the number of competitive bids. Furthermore, asthe material must arrive at the place of laying in a hot condition, it'

is frequently overheated, if the haul be a long one, th us killing? theasphalt cement and causing the pavement to crack.

Asphaltic concrete pavements difier from sheet asphalt pavements abovereferred to merely 'in the fact that the mineral aggregate employed iscoarser, running from 2c, 1926. Serial m. 97,767.

inch down to filler and graded according to specifications; the asphaltcement employed is similar to that used in the previous type of pavementbut is generally softer.

Obviously themethod of preparing and lay-' ing this type of pavement isopen to the same objections as above indicated in connection with sheetasphalt pavements.

As hereinbeforastated it is the object of the present invention toprepare at a central plant, "asphaltic materials containing all of thenecessary ingredients for sheet asphalt pavements and asphaltic concretepavements; such materials being prepared and combined in a mannerwhich-will prevent pack ing thereof during shipment or while standing inthe contractors stockpile and to which it is only necessary to applyheat by t-he local contractor at the time the material is spread on thesubgrade.

"In the preparation of 'material'for the, construction of sheet asphaltpavement I add to a dry, satisfactorily graded sand or combination ofsands, with or withoutfiller in accordance with the governingspecifications, a dry pulverized asphalt, and the two thoroughly mixed;the amount added being controlled by factors which will be explainedhereinafter. phalt may be a natural hard bitumen of the class known asasphaltites, such as gilsonite, grahamite, manjak, etc., or a residualas phalt produced from an asphaltlc base or a mixed-base oil by theusual refiner methods of removing by volatilization t e lighter portionsuntil the residue is one that can be ground to a non-adherent powder, ora sulphonated residual asphalt, the hardness of which is obtained by.the llltIOdllGtlOH of sulphur, or a combination of an asphaltite with aresidual asphalt or naturalasphalt made by melting the constituentstogether in such proportions that when cold the material may be groundto a non-adherent powder. 4 1

Of all of these natural, artificial or combined materials gilsonitegives the best results and I prefer it althoughl do not limit myself tousing it only, as satisfactory pavements can be made with others. Thehard asphalt may be ground to pass any mesh screen considered necessary,but I have This pulverized asfound that passing a 60 mesh screen issufliciently fine. a

The sand and filler (mineral aggregate) may be heated prior to theintroduction of the powdered asphalt or the combined ma terials heatedduring the mixing operation, or after being mixed, as desired, but thetemperature to which it israised must not exceed that at which thepulverized hard asphalt will blend with the soft asphalt or flux used inthe step to follow. This temperature cannot be given for allcombinations as it will depend upon the kind of hard asphalt used; forexample, gilsonite will blend with the flux at 250 'to 300 Fahrenheit,While a residual asphalt of suflicient hardness to permit grinding to anon-adherent powder will require 325 to 375 Fahrenheit to cause it toblend with the flux, while grahamite will require 400. maximumtemperature at which the mixture of mineral aggregate and dry asphaltmay be raised can best be defined as about 25 below the point at whichthe dry asphalt used blends with the flux and must be'determined byexperimentation with the materials 'to be employed. Obviously it is notessential to heat the dry mixture to this point as the flux can beincorporated at a lower one, but the higher the temperature the morethoroughly and easily can the flux be mixed with the dry materials. Theheating and mixing of the dry materials may be performed in any type ofmachine suitable for the purpose, such as a revolving drum heater, aheated batch mixer or a heated spiral conveyer with special blades which1 prefer.

To the heated mixture of the mineral aggregate and the dry asphalt isnext added the semi-liquid asphaltic flux heated to approximately thesame temperature and thoroughly mixed therewith; the amount added beingcontrolled by factors which will be. explained hereinafter. This fluxmay be a natural soft asphalt or the residue from an asphaltic-or amixed-base oil produced by any of the usual refinery methods. It should,however, have a flash-point above the temperature at which it is to beraised and its viscosity should not be so great as to render thefinished product gummy or objeetionably sticky for handling. For thepurpose of identification the semi v liquid asphalt or flux may bedescribed as having a specific gravity of 12 to 14: degrees Baum; aflash point not under 300 degrees Fahrenheit; loss upon heating at 325degrees Fahrenheit for5 hours not over 5% asphaL t1c content 80% or overand not under 98% soluble in carbon disulphide. Such a semi-- liquidasphalt or flux is the one I prefer to use but as other semi-liquidasphalts or asphaltic fluxes of a similar composition andcharacteristics conldbe used I do not want to be considered as limitingmyself to the use of this specific flux. The mixing of the flux The withthe drymaterials may be done in a suitable machine such as the usualpug-mill or a similar paddle or worm mixer, or a depend upon threefactors; first, the desired or specified percentage of asphalt asasphalt cement in the finished pavement; second, the desired orspecified penetration of the asphalt as asphalt cement in the finishedpavement; and third, the relative proportions of the hard. asphalt andflux employed that are required to produce asphalt cement of thispenetration.

For example, is the specifications covering the finished pavement callfor 10% 0fasphalt as asphalt cement having a penetration of 4050 at 77Fahrenheit and it is desired to use gilsonite as the hard asphalt and acentain asphaltic flux having the desired flash point and viscosity; itis found by experimentation that 30 parts of gilsonite and 0 parts ofthis flux will produce an asphalt cement having the penetration desired.if the specifications call for 10% of asphalt cement in the finishedpavement the proportional mixture and the method of making a one tonbatch-of material to meet the specifications would be: 60 pounds ofpowdered gilsonite mixed with 1800 pounds of sand and filler, themixture'heated and 140 pounds of flux added and thoroughly incorporated.

If grahainite is used in place of gilsonite the'proportions of the hardasphalt,-i. e.,.

the grahamite, to the flux would be less while with a residual asphaltit might be greater; any given combination being determined by the usualtesting methods.

The composition just described constitutes the shipping product and uponleaving the mixer it is loaded directly into cars, trucks or wagons fortransportation or deposited in a stock pile "for future shipping.

As will readily be seen, this product contains the specifiedv amount orpercentage of asphalt, but as the hard asphalt remains inactive orunblended with the flux, and the flux remainsunstifi'ened by the hardasphalt and will so-reinain until the material has been heated to theblending point of the large a stock at the railroad yard as he shoveledinto'the bucketelevator of a simple heating machine. The heating machinemay be of anysuitable type but should consist in general of a bucketelevator which carries the material to a small hopper located. above theheater" proper and a suitable automatic feeder that regulates the flowof material from the hopper to the 'heater proper;

The heater may be of the revolving drum type, the/pan and rake type, aspiral conveyer type, or any type of concrete mixer equipped with aproper. burner; in either case-it should be preferably heated by an oil"burner. The flow of the material through the heater and also the heatfrom the burner are regulated so-that the inaterial passing through isheated to at least 50 above the blending point of the hard asphalt usedand the flux. This heatingcauses the hard asphalt and the flux to becomeblended into "The machine should have a capacity equal a true asphalticcement meeting any specification necessary and of a superior quality.

I to the maximum quantity it is desired to handle per day asthe outputof a large machine can be reduced by regulating the 7 feeder and the oilburner.

Upon leaving the heater the hot material may fall upon a shoveling sheetor platform at the rear of the apparatus. From this platform it may bespread withshovels,

raked and rolled in the usual manner.

1 My process of making asphaltic. concrete pavement material isessentially the same as that just described, except that the mineralaggregate includes properly graded crushed stone in addition to the sandand filler and usually the asphalt cement employed will be slightlysofter than that used'in sheet asphalt pavements; this simply requires adiiferent proportion of the hard asphalt and the flux. This asphalticconcrete material may also be shipped as a non-packing ma t'erialcontaining all of the necessary ingredients of the finished pavement andmay be heated at the point of application in the same type of heater andspread, raked and rolled hot in the usual manner.

From the foregoing description it will be apparent to those skilled inthe art that I have devised a method of preparing paving material whichapplies equally well to sheet asphalt pavements and asphalt concretepavements; that the materials produced by the process due to thepresence of the un' blended asphalt may be shipped or stored in stockpiles withoutpacking; that the. ma-

terials are self contained, i. a, require no additions of material bythe road engineer but simply that the material be heated to a isintended to include .materi'als such as sand, limestone dust or otherfiller, crushed stone, etc. I

In accordancewith the patent statutes I have described what I nowbelieve to be the best embodiment of the invention, but I do not wish tobe understood thereby as limiting myself or the scope of the "invention,as many changes and modifications may be made without departing from thespirit of the invention; all such I aim to include in the scope of-theappended claims.

What I claim'as new and desire to secure by Letters Patent is:

1. The process of preparing asphaltic road material for storage andshipment the asphalts ofwhich are adapted to be converted to anasphaltic cement on the job by, blending, which comprises mixing mineralaggregate with hard asphalt in a powdered form in insuflicient quantityto provide the required percentage of asphaltic cement, said mixingbeing carried out at a temperature below that at which the hard as haltblends with a soft asphalt, and then a ding semi-liquid asphalt orasphaltic flux to bind the powdered asphalt particles on the surface ofthe aggregate, the quantity of semiliquid asphalt or asphaltic fluxbeing sulficient to provide the desired percentage of asphaltic cementwhen blended with the ing the same and adding the semi-liquid asphalt orasphaltic flux. I

road material for storage and shipment the asphalts of which are adaptedto be con-: Vertedto an asphaltic cement on the job by blending, whichcomprises heating the mineral aggregate and a powdered hard asphalt to atemperature below the point atuse 3. The process of preparing, asphaltie-.which the hard asphalt will blend with a semi-liquid asphalt orasphaltic flux, mixing the same, heating the desired amount of thesemi-liquid asphalt or asphaltic flux to substantially the sametemperature and mix: ing with the aggregate and hard asphalt.

4. A composition of matter adapted for shipping, said compositioncomprising a loose, granular, non-compacted mass adapted for paving, thegranules of said mass composed ofmineral aggregate coated with hard,powdered asphalt particles and bound thereto by a coating of ,asphalticflux.

5. A; composition of matter adapted-for shipping, said compositioncomprising a loose, granular, non-compacted mass of graded mineralaggregate, -a coating of powdered hard asphalt particles on the granulesof said aggregate, and a coating of asphaltic flux binding said coatingof powdered hard asphalt to the aggregate.

. 6. A composition of matter adapted for a e ate- ,1

ggr WILLIAM 0. WEST.

